1. Field of the Invention
The present invention relates to a work vehicle and in particular to a crawler work vehicle that travels using a crawler and is steered using a steering clutch and a steering brake.
2. Background Information
Power from an engine in a bulldozer, which is an example of a crawler work vehicle, is transmitted through a transmission to left and right drive wheels so that the left and right crawlers are driven. This type of bulldozer is provided with steering clutches and steering brakes corresponding to the left and right drive wheels. Left and right turning is conducted by controlling the left and right steering clutches and steering brakes with hydraulic pressure (see for example Japanese Patent Publication H8-18573).
For example, when gently turning left, the left side steering brake is set to a half-engaged condition and the left side steering clutch is disengaged while the right side steering clutch is engaged and the right side steering brake is disengaged.
Under such a condition, slippage occurs in the left side steering brake since the left side steering brake is in a half-engaged condition. Therefore, if such a condition continues for a long time, there is a problem that a thermal load on the left side steering brake increases and the steering brake is scorched.
Accordingly, in a control device on the vehicle of the Japanese Laid-open Patent 2010-144598, the engine speed is decreased to protect the steering brake when the vehicle is detected to be descending a slope with a certain angle of inclination or greater in a state in which a high gear speed is selected and when the engine rotation speed exceeds a certain rotation speed during a turning operation.
In a control device in the vehicle of the Japanese Laid-open Patent 2010-144816, when the vehicle is detected to be descending a slope with a certain angle of inclination or greater during a turning operation with a lock-up clutch in an engaged state, the lock-up clutch is disengaged. As a result, since the power is transmitted through a torque converter, the load is absorbed by the torque converter and the load on the steering brake is reduced to protect the steering brake.